Simultaneous finning and reforming of tubular heat transfer surface

ABSTRACT

An improved machine for forming integral, radially extending, helical fins on tubes incorporates a novel spindle which both forms and then modifies the fins after they are formed to improve heat transfer characteristics of the tubing. Two modifying operations, knurling and bending or shaping the newly formed helical fins, are shown. The improved spindle can be utilized on virtually all finning machines to produce tubing of desired geometry.

States Patet U n lte [72] inventors William A. King;

Chester D. Ware, both 01 La Crosse, Wis. [21] App]. No. 812,053 [22] Filed Apr. 1, 11969 [45] Patented Aug. 31, 19711 73] Assignee The Trane Company La Crosse, Wis.

[54] SIMIUILTANEOUS FINNING AND REFORMING 0F TUBULAR HEAT TRANSFER SURFACE 6 Claims, 6 DrawingFigs.

[52] US. Cl 72/98, 29/ 157.3 AH [51] Int. Cl. B2ll1 3/00 [50] Field 01 Search 72/77, 78,

References Cited UNITED STATES PATENTS 1,909,005 5/1933 Paugh 29/157.3 3,326,283 6/1967 Ware 165/184 3,383,892 5/1968 Brothen. 29/157.3 3,383,893 5/1968 Counts 72/98 FOREIGN PATENTS 595,680 12/1947 Great Britain 165/184 Primary Examiner-Lowell A. Larson Attorneys-Carl M. Lewis and Arthur 0. Andersen ABSTRACT: An improved machine for forming integral, radially extending, helical fins on tubes incorporates a novel spindle which both forms and then modifies the fins after they are formed to improve heat transfer characteristics of the tubing. Two modifying operations, knurling and bending or shaping the newly formed helical fins, are shown. The improved spindle can be utilized on virtually all finning machines to produce tubing of desired geometry.

PATENTEU M1831 :97: 3.502.027 sum 1 UF 2 FlG-l I6 'IIII'IIIIIIIIII'! "llllml'il INVENTOR. WILLIAM A. KLue BY CHESTER D. WARE.

PATENTEU M1831 l9?! SHEET 2 [IF 2 3'602'027 INVENTOR.

\mLuAn A. KLus BY CHESTER awake QRNET SIMULTANEOUS FINNING AND REFORMING OF TUBULAR HEAT TRANSFER SURFACE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the manufacture of integrally finned heat transfer tubing, and more particularly to an improved too] arrangement for use in a fin-forming machine.

2. Description of the Prior Art In conjunction with certain uses of integrally finned heat transfer tubing, it is desirable to alter the surface characteristics of the fin periphery. In fact, for certain applications greater heat transfer rates can be achieved with a modified fin surface. For example, see US. Pat. No. 3,326,283 which discloses a knurled, integrally finned heat transfer surface which displays improved heat transfer properties. One method for producing a surface of the type described therein is to process finned tubing through a separate machine on which the knurling operation is performed. This operation requires removing the tube from the finning machine and transferring it to a different machine, doubling the labor requirement for producing a modified, integrally finned tube.

Another method available for producing a knurled fin surface or a rolled over fin surface is to mount a second head on a fin-forming machine which follows the fin-fonning head. This second head would contain knurling or roll over dies which operate on the fin entirely independent of the fin'forming dies. This machine by necessity is both costly and complex to operate because the fin-forming head and fin-reforming head must be capable of independent operation.

SUMMARY OF THE INVENTION This invention encompasses a novel fin-forming machine which simultaneously forms an integral fin on a tube and reforms or shapes the fin geometry in a single operation. This invention eliminates the need for two machines to manufacture the desired tube surface; it also eliminates the need for the more complex machine which carries both a fin-forming and a reforming head.

The present invention provides an improvement in an apparatus for forming radially extending, helical fins from tubular stock, the apparatus including base means for holding a tube, a head mounted on the base means and having at least one spindle rotatably mounted thereon, means for providing relative rotary motion between the head and the tube about a common axis, means for providing relative longitudinal motion between the head and the tube, the improvement comprising: a plurality of disc dies axially mounted on the spindle, a fin-reforming die mounted on the spindle and axially spaced from at least a portion of the plurality of disc dies, the reforming die axially positioned on the spindle to modify the fin geometry after the disc dies have formed the helical fin, the reforming die including surface means for substantially modifying at least a portion of the helical fin geometry formed by the disc dies away from its characteristic radially extending configuration.

The reforming die can be in the form of a knurling die, a rollover die, or any other die which substantially modifies the geometry of the helical fin formed on a tube.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a partially schematic illustration of a fin-forming machine incorporating the tool arrangement of the present invention.

FIG. 2 is an illustration of two spindles forming and reforming fins on a tube. Each of the spindles carry a plurality of disc dies and a knurling die.

FIG. 3 is an end elevation view of FIG. 2 taken along line 33.

FIG. 4 is a side elevation view, in partial cross section of two spindles operating to form and reform fins on a tube. Each of the spindles contain a plurality of fin-forming dies and a rollover die.

FIG. 5 is an end elevation view of an operation similar to FIG. d, except that three spindles are illustrated spaced about apart.

FIG. 6 is a partially schematic illustration of a rotary head fin-forming machine containing the spindles of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A finning machine of the fixed head, driven spindle type is illustrated in FIG. 1. Finning head 5 is fixedly attached to support bar 6, which is connected to base 2. A tube 9 to be finned in the machine has one end positioned in support 3; the other end extends through the finning head and into support It). The tube is allowed to freely rotate and move axially within supports 3 and 110.

Head 5 carries a spindle ill in its upper portion 112 and a second spindle 13 mounted in its lower portion 14. Spindles Ill and 13 are mounted in bearings contained in head 5. The head 5 can also contain means (not shown) for vertically separating spindles I1 and 13 to allow positioning and removal of the tube 9. Spindlell is driven through shaft 15 by belt and pulley arrangement 16, which is in turn driven by an electric motor or other suitable drive means 117.

If necessary, a mandrel 118 can be positioned inside tube 9 to prevent undesirable distortion of the tube during the finning and reforming process. The mandrel. I3 is held in position in tube 9 by a support arm 19 secured to base 2. A set screw 7 is provided to secure mandrel 118 in support 119.

In operation the finning machine of FIG. ll simultaneously extrudes and reshapes or reforms helical fins 30. Driven spindle 11 causes tube 9 to rotate as the fins are being formed. The fin-forming process automatically advances tube 9 in the direction of arrow 8.

Spindles II and 113 are better illustrated in FIG. 2. Referring now to that figure, spindles 11 and llli are mounted on shafts l5 and 25. Shaft 15 is driven by motor means 17 (shown in FIG. 1), while shaft 25 is allowed to freely rotate. Mounted on spindles Ill and 13 are three distinct sets of dies. The first die 26 has a frustoconical shape with a smooth surface. This portion of the die reduces the diameter of the tube as the spindles move longitudinally along the tube surface. The second die set consists of a plurality of roller die discs 27 which are axially spaced along the spindle by spacers 23. One disc die can be axially spaced from another by spacers 28, or if the spacers and die are of unitary construction, by the hub portion of the die which would be of greater width than the die surface. The disc dies 27 gradually increase in diameter from the one nearest die 26 to the last disc die. Thus the disc dies can form a fin of gradually increasing depth as the spindles move longitudinally along the tube.

The last die mounted on spindles 11 and i3 is one which modifies the fin geometry after it has been fully formed by the disc dies. In FIG. 2 the reforming die 29 is shown as a longitudinally serrated knurling die. The teeth of knurling die 29 form indentations in the periphery of newly formed fins 30. Knurling die 29 can be mounted to freely rotate on spindle 11, although preferably it is rigidly connected to spindle 11 to aid rotation of tube 9, since the tube relies on the spindles II for rotation. Spindle 113 contains a knurling die 31 substantially identical to die 29. knurling die 31 is preferably mounted for free rotation on spindle 13, especially if die 29 is rigidly connected to spindle 11. A mandrel 12 is shown in its position inside tube 9.

FIG. 3 is an end view of FIG. 2 along line AA. The descriptive numerals used in FIG. 3 are the same as those used in FIG. 2. It can be seen in FIG. 3 that a key 32 rigidly connects all of the dies to spindle 11. However, no key is inserted through knurling die 31 thus allowing it to freely rotate on spindle 13.

A 'collar 34 can be inserted onto spindle 13 to prevent knurling die 31 from sliding ofi spindle 13.

FIG. 4 illustrates a spindle arrangement similar to that shown in FIG. 2, except that the knurling die has been replaced by reforming dies 35 and 36. Reforming dies 35 and 36 roll the fins 37 over toward the next adjacent fin. Dies 25 and 27 remain the same as shown in FIG. 2. The die surface of rollover die 35 is the first shaping surface to contact a newly formed fin. The surface of die 35 partially bends the fins. The surface 38 of die 36 is suitably shaped relative to its predecessor 35 to further roll the fins 37 toward the next adjacent fin. The die surfaces of reforming dies 35 and 36 can be either straight or curved in cross section, depending upon the final fin geometry which is desired.

Instead of utilizing only two spindles as shown in FIGS. 1 through 4 an arrangement employing three spindles mounted approximately 120 apart is illustrated in FIG. 5. Spindles 40, 41 and 42 can be mounted in the same type of head as illustrated in FIGS. 1 and 6. Spindle 42 is shown carrying a knurling die 43 along with die discs 44. It is, of course, un-

. derstood that the number of spindles depends upon the particular application and the availability of a suitable fin-forming machine. The two spindle arrangements shown in FIGS. 1 through 4 and FIG. 6 are illustrated as such only for simplicity.

The two difierent reforming dies illustrated are not the only variations which can be utilized in this invention. Other dies which provide different fin configurations can easily be substituted for the reforming dies shown. For example, a die which produces a corrugated effect in the fin can be inserted on the spindles described in place of the knurling or rollover dies. In addition, the reforming dies canbe mounted for rotation on the spindles or can be rigidly connected thereto, for example by a key. Whether they are so connected depends upon the particular reforming or shaping die being used, the type of fin-forming machine in which the spindles are inserted and the desired geometry of the fin.

A finning machine which operates differently from the one shown in FIG. 1 is illustrated in FIG. 6. A housing 55 for finning head 56 is fixedly attached to support base 52. A tube to be finned 60 is inserted through tube support 53 and into finning head 56. A mandrel 70 is inserted through support 53, through the finning head and into tube 60. The mandrel prevents undesirable distortion of the tube during the finning and reshaping process. The mandrel is removably attached by set screw 80 to support arm 81, which in turn is rigidly secured to base 52.

The tube 60 is advanced through the finning machine in the direction of the arrow 59. A threaded drive rod 54 is mounted for rotation in base 52. Means for rotating the drive rod (not shown) is enclosed in base 52. Arm 82, removably attached to tube 60 by means of set screw 83, has attached to its lower portion threaded driven nuts 84. As drive rod 54 rotates, the tube is moved through the finning head.

Finning head 56 has a hub portion 62 surrounding tube 60 which is rotatably mounted in housing 55 on bearing surface 63. Hub 62 is driven by belt and pulley arrangement 64, which is in turn driven by an electric motor 65. Pivotally mounted on hub 62 at points 66 are spindle carrying chuck sections 67 and 68. A slide ring 69 (shown in cross section) surrounds the arms of chuck portions 67 and 68. Die carrying spindles 71a and 71 are rotatably mounted in chuck portions 67 and 68. The spindles are allowed to freely rotate in their mountings.

As slide ring 69 is moved toward the spindles, the dies on spindles 71a and 71 begin the fin-forming and reforming operation on the tube. The reforming dies 75 can be either freely rotating about or rigidly connected to the spindles as the application requires. As can been seen, the finning machine of FIG. 6 differs from that in FIG. 1 in that the entire head assembly 56 rotates about tube 60.

What is claimed is: I

1. In an apparatus for forming radially extending, helical fins on the exterior surface of tubular stock, said apparatus including a base, suppprt means communicating with said base for supporting a tu e to be finned, head means operatively connected to said base and having at least one spindle rotatably mounted thereon, drive means for providing relative rotary motion between said spindle and said tube, and a plurality of fin-forming dies axially mounted on said spindle for sequentially engaging said tube to form a helical fin thereon, the improvement comprising:

a fin-reforming die mounted on said spindle axially spaced from said fin-forming dies, said fin-reforming die having a fin engaging surface for engaging the fin helix along substantially the entire length of the tube and thereby modifying the fin configuration without interrupting the continuous fin helix.

2. The apparatus according to claim 1 wherein said fin engaging surface is longitudinally serrated, said fin-reforming die being oriented on said spindle so that the serrations are transverse to said fins whereby the edge portions of said fins are knurled by said fin-reforming die.

3. In an apparatus for forming radially extending, helical fins on the exterior surface of tubular stock, said apparatus in cluding a base, support means communicating with said base for supporting a tube to be finned, head means operatively connected to said base and having at least one spindle rotatably mounted thereon, drive means for providing relative rotary motion between said spindle and said tube, and a plurality of fin-forming dies axially mounted on said spindle for sequentially engaging said tube to form a helical fin thereon, the improvement comprising:

a fin-reforming die mounted on said spindle axially spaced from said fin-forming dies, said fin-reforming die having an inclined surface for engaging a segment of said helical fin and bending it toward the next adjacent segment in a continuous manner along the fin helix.

4. The apparatus according to claim 3 wherein said inclined surface is inclined linearly in a direction away from said fin helix.

5. The apparatus according to claim 3 wherein said inclined surface is concave.

6. The apparatus according to claim 3 wherein said head means has first and second spindles rotatably mounted thereon, each of said spindles having axially spaced fin-forming dies and a fin-reforming die mounted thereon, said finreforming die of said first spindle having a linearly inclined surface for engaging a segment of said helical fin and bending it toward the next adjacent segment in a continuous manner, said fin-reforming die of said second spindle having a concavely inclined surface for engaging said segment of said fin previously engaged by said first fin-reforming die, said second finreforming die rolling said segment further toward the next adjacent segment in a continuous manner. 

1. In an apparatus for forming radially extending, helical fins on the exterior surface of tubular stock, said apparatus including a base, support means communicating with said base for supporting a tube to be finned, head means operatively connected to said base and having at least one spindle rotatably mounted thereon, drive means for providing relative rotary motion between said spindle and said tube, and a plurality of fin-forming dies axially mounted on said spindle for sequentially engaging said tube to form a helical fin thereon, the improvement comprising: a fin-reforming die mounted on said spindle axially spaced from said fin-forming dies, said fin-reforming die having a fin engaging surface for engaging the fin helix along substantially the entire length of the tube and thereby modifying the fin configuration without interrupting the continuous fin helix.
 2. The apparatus according to claim 1 wherein said fin engaging surface is longitudinally serrated, said fin-reforming die being oriented on said spindle so that the serrations are transverse to said fins whereby the edge portions of said fins are knurled by said fin-reforming die.
 3. In an apparatus for forming radially extending, helical fins on the exterior surface of tubular stock, said apparatus including a base, support means communicating with said base for supporting a tube to be finned, head means operatively connected to said base and having at least one spindle rotatably mounted thereon, drive means for providing relative rotary motion between said spindle and said tube, and a plurality of fin-forming dies axially mounted on said spindle for sequentially engaging said tube to form a helical fin thereon, the improvement comprising: a fin-reforming die mounted on said spindle axially spaced from said fin-forming dies, said fin-reforming die having an inclined surface for engaging a segment of said helical fin and bending it toward the next adjacent segment in a continuous manner along the fin helix.
 4. The apparatus according to claim 3 wherein said inclined surface is inclined linearly in a direction away from said fin helix.
 5. The apparatus according to claim 3 wherein said inclined surface is concave.
 6. The apparatus according to claim 3 wherein said head means has first and second spindles rotatably mounted thereon, each of said spindles having axially spaced fin-forming dies and a fin-reforming die mounted thereon, said fin-reforming die of said first spindle having a linearly inclined surface for engaging a segment of said helical fin and bending it toward the next adjacent segment in a continuous manner, said fin-reforming die of said second spindle having a concavely inclined surface for engaging said segment of said fin previously engaged by said first fin-reforming die, said second fin-reforming die rolling said segment further toward the next adjacent segment in a continuous manner. 